The invention relates to the synthesis of polybenzoxazole (PBO), polybenzimidazole (PB) or polybenzothiazole (PBT) and related polymers (hereinafter referred to as PBZ polymers).
PBZ polymers are a known class of polymers which contain a plurality of mer units comprising at
(1) a first aromatic group (Ar.sup.1); and PA1 (2) a first azole ring which is fused with the first aromatic group. PA1 (3) a second azole ring which is fused with the first aromatic group, and PA1 (4) a divalent group (DL), which is inert with respect to all reagents for making PBZ polymers under polymerization conditions. bonded by a single bond to the 2-carbon of the second azole ring PA1 DL is a divalent group as previously described: and PA1 each Z is independently chosen from the group consisting of --O--, --S-- or --NR--, wherein R is an aliphatic or aromatic group which does not interfere with polymerization. PA1 (1) a first aromatic group (Ar.sup.1); PA1 (2) a first o-amino-basic moiety bonded to said first aromatic group, which o-amino-basic moiety contains: PA1 (3) an azole-forming group bonded to the first aromatic group which is either a second o-amino-basic group or an "electron-deficient carbon group", PA1 (1) a divalent group which is inert with respect to all reagents under reaction conditions; PA1 (2) an "electron-deficient carbon group", such as a carboxylic acid or acid salt; and PA1 (3) an azole-forming group which may be a second "electron-deficient carbon group" or, if the divalent group comprises an aromatic group, an o-amino-basic group. PA1 each Z is an oxygen atom, a sulfur atom or --NR--, wherein g is an aliphatic or aromatic group which does not interfere with polymerization and each Z is bonded to the first aromatic group (Ar.sup.1) ortho to a primary amine group (in the monomer) or the nitrogen atom of the azole ring in which it is located (in the polymer); PA1 DL is a divalent group as previously described: and PA1 each Q is an electron-deficient carbon group as previously described. PA1 (1) an azole-containing compound having: PA1 (c) a leaving group bonded to said aromatic group in a position such that it is activated by said azole ring, PA1 (2) a displacing compound having: PA1 (1) an organic moiety which is inert with respect to all reagents under reaction conditions: and PA1 (2) two reactive groups selected, such that a polymer is formed, from the class consisting of: PA1 (1) a first aromatic group; PA1 (2) an azole ring fused to said first aromatic group; PA1 (3) a second aromatic group bonded to the 2-carbon of said azole ring; PA1 (4) a leaving group bonded to said second aromatic group in a position where it is activated by said azole ring; PA1 (5) a nucleophilic moiety, as previously defined, linked to said first aromatic group in a position not ortho to the 4- or 5-carbon of the azole ring; and PA1 (6) a counter-moiety, as previously defined, bonded to said nucleophilic moiety. PA1 (1) an unfused first aromatic group (Ar.sup.1), which comprises two aromatic moieties (Ar.sup.1a and Ar.sup.1b) linked by a bond or a divalent linking moiety (D) which is inert with respect to nucleophilic aromatic substitution; PA1 (2) a first azole ring fused with one aromatic moiety (Ar.sup.1a) of said unfused first aromatic group, and a second azole ring fused with the other aromatic moiety (Ar.sup.1b) of said unfused first aromatic group; PA1 (3) a second aromatic group (Ar.sup.2) bonded to the 2-carbon of said first azole ring and a third aromatic group (Ar.sup.3) bonded to the 2-carbon of said second azole ring; and PA1 (4) a first leaving group bonded to said second aromatic group and a second leaving group bonded to said third aromatic group. PA1 (1) a first aromatic group; PA1 (2) an azole ring fused to said first aromatic group; PA1 (3) a second aromatic group bonded to the 2-carbon of said azole ring; and PA1 (4) an oxygen, sulfur or nitrogen atom linked to said first aromatic group and bonded by a single bond to a second aromatic group of an adjacent unit. PA1 (1) a first aromatic group; PA1 (2) an azole ring fused to said first aromatic group; PA1 (3) a second aromatic group bonded to the 2-carbon of said azole ring; and PA1 (4) an oxygen, sulfur or nitrogen atom linked to said first aromatic group and bonded by a single bond to a second aromatic group of an adjacent unit.
Each mer unit preferably further comprises
Those mer units ordinarily comply with one of the two formulae ##STR1## wherein: Ar.sup.1 is a first aromatic group as previously described;
PBZ polymers, their chemical structure, their properties and their synthesis are described in depth in numerous references such as 11 Ency. Poly. Sci & Eng., Polybenzothiazoles and Polybenzoxazoles, 601 (J. Wiley & Sons 1988: Wolfe et al., Liquid Crystalline Polymer Compositions and Process and Products, U.S. Pat. No. 4,703,103 (Oct. 27, 1987); Tsai et al., Method for Making Heterocyclic Block Copolymer, U.S. Pat. No. 4,578,432 (Mar. 2, 1986); Wolfe et al., Liquid Crystalline Poly(2,6-Benzothiazole) Compositions, Process and Products, U.S. Pat. No. 4,533,724 (Aug. 6, 1985); Wolfe, Liquid Crystalline Polymer Compositions, Process and Products, U.S. Pat. No. 4,533,693 (Aug. 6, 1985) and Wolfe et al., Liquid Crystalline Polymer Compositions and Process and Products, U.S. Pat. No. 4,533,692 (Aug. 6, 1985), which are incorporated herein by reference.
It is known in the art to synthesize PBZ polymers by the reaction of a first monomer comprising:
(a) a primary amine group bonded to the first aromatic group: and PA2 (b) a hydroxy, thio or amine group bonded to the first aromatic group in ortho position with respect to the primary amine group; PA2 (a) an azole ring: PA2 (b) an aromatic group bonded to the 2-carbon of said azole ring: and PA2 (a) an organic moiety which is not electron-withdrawing and which is inert with respect to all reagents under reaction conditions; PA2 (b) a nucleophilic moiety linked to said organic moiety, which nucleophilic moiety is a nitrogen atom having a hydrogen atom or inert organic substituent or an oxygen atom or a sulfur atom; and PA2 (c) a counter-moiety bonded to said nucleophilic moiety which can easily be removed therefrom, PA2 (a) azole-containing groups having: an azole ring bonded to said organic moiety, an aromatic group bonded to the g-carbon of said azole ring, and a leaving group bonded to said aromatic ring in a position where it is activated by said azole ring: and PA2 (b) displacing groups having: a nucleophilic moiety, which is an oxygen atom, a sulfur atom or a nitrogen atom, bonded to said organic moiety: and a counter-moiety bonded to said nucleophilic moiety,
and a second monomer comprising:
The known syntheses for PBZ polymers ordinarily conform to one of the following two formulae: ##STR2## wherein: each Ar.sup.1 is a first aromatic group:
Those polymerizations have a number of drawbacks. First, polymerization is ordinarily carried out in a strong mineral acid such as polyphosphoric acid or a mixture of methanesulfonic acid and phosphorus pentoxide. Such acids are difficult to work with and must be washed from the resulting polymer by time-consuming rinsing over periods as long as 24 hours or longer. Second, monomers containing the o-amino-basic group are oxidatively unstable and must be stored as hydrogen halide salts, which are converted back to the basic monomer in the polymerization vessel by a time-consuming dehydrohalogenation step. Third, in the known syntheses the concentration of solids in the reaction mixture cannot ordinarily exceed 10 to 15 percent, so that large reaction vessels are necessary to synthesize small amounts of polymer.
What are needed are alternative processes for synthesizing PBZ polymers which do not rely upon the reaction of an o-amino-basic group with an electron-deficient carbon group to link monomers and which can avoid some or all of the drawbacks of the prior art processes.